Liquid ring machines are known per se, and conventionally comprise a vaned rotor which is rotatable within a cylindrical drum with the ends of the vanes being maintained in contact with a liquid ring during such rotation. The liquid ring forms a closed chamber with each pair of adjacent vanes on the rotor, and the volume of this chamber varies in dependence on the angular orientation of the rotor due to the fact that the axis of rotation of the rotor is offset from the central axis of the drum. It will be appreciated that such a machine may be used either to compress a working fluid or to provide controlled expansion of the fluid depending on the angular positions at which the fluid depending on the angular positions at which the fluid is introduced into, and discharged from, each chamber.
The functioning of such a liquid ring machine is well known in the art. However, the application of such machines is limited by the fact that they are generally of relatively low efficiency compared with other types of machine, the best efficiency of a typical machine generally being no more than about 50%.
A significant factor affecting the efficiency of such machines is the severe mechanical losses which arise due to the drag on the rotating liquid ring exerted by the adjacent walls of the outer drum. WO 89/12168, published 14 Dec. 1989, discloses a liquid ring compressor in which the drum is rotatable with the liquid ring to reduce the drag on the liquid ring.
It is an object of the invention to provide a liquid ring thermodynamic machine of increased efficiency.